In electrical power supply systems, in particular power supply systems for the transmission of electrical power whose voltage changes periodically and in which the current flowing through the power supply system changes periodically, it is desirable to be able to predict future voltage and/or current waveforms. During undisturbed operation, the voltage and the current oscillate periodically at a constant frequency, with a constant amplitude, about a defined zero position. A phase shift can occur between the phase angle of the voltage and the phase angle of the current as result of electrical systems being connected to an electrical power supply system. Depending on the electrical systems which are connected, different phase shifts occur between the current and the voltage. In addition, voltage spikes and changes in the periodicity of the current and voltage or else transient processes can occur as a result of unpredictable events, such as switching overvoltages, which are produced when switching processes take place in the electrical power supply system, or else lightning strikes on the electrical power supply system. For certain applications, it is necessary, even in the case of waveforms which differ to a major extent from the fundamental oscillation, to determine in advance the actual waveform of the current and voltage in the electrical power supply system, in terms of the phase angles, in particular the zero crossings, as well as their amplitudes.
Fourier transformations are used, for example, in order to predict the current and/or voltage waveform in an electrical power supply system. Fourier transformations are used in an attempt to model the voltage and current waveforms which actually occur in the electrical power supply system by means of a large number of known functions that are superimposed on one another, and this is used to predict the future waveform of the voltage or of the current in an electrical power supply system. The calculations that are required for this purpose are associated with a quite considerable time requirement even when using the very latest computer technology.
Patent Abstract of Japan, JP 2055528, discloses the use of measured information to determine a future system voltage.
It is also known for a Prony method to be used to determine power supply system equivalents (Hong, J.-H, Park, J.-K., “A Time-Domain Approach To Transmission Network Equivalents Via Prony Analysis For Electromagnetic Transients Analysis”. IEEE Transactions on Power Systems, Vol. 10, 1995, No. 4, pages 1789-1797). According to Amano, M., Watanabe, M., Banjo, M., “Self-Testing And Self-Tuning Of Power System Stabilizers Using Prony Analysis”, Power Engineering Society 1999 Winter Meeting, ISBN 0-7803-4893-1, pages 655-660, it is known for the Prony method to be used for the configuration of regulators.
According to Lobos, T., Rezmer, J., Koglin, H.-J., “Analysis of Power System Transients Using Wavelets and Prony Method”, Power Tech Proceeding, September. 2001, ISBN 0-7803-7139-9, it is known for a comparison to be carried out between the Prony method and the Fourier analysis.